The ordinary construction for a vehicle having an internal combustion engine includes an exhaust system for handling exhaust gases. Typically, the exhaust system includes an exhaust pipe for directing exhaust gases from the internal combustion engine to a muffler, the gases then flow to a tail pipe and into the surrounding atmosphere. There may be additional pieces of equipment in series with the muffler, such as, a catalytic converter and a resonator. The desire of some vehicle designers to make vehicles low has resulted in some instances of having the muffler positioned immediately adjacent to the underside of a passenger compartment. The proximate positioning of the muffler to the passenger compartment has led to a recognition of the desirability of positioning a heat shield between the muffler and the passenger compartment.
The use of heat shields on vehicular mufflers is taught in U.S. Pat. No. 4,478,310, issued to Donald P. Harter on Oct. 23, 1984, entitled "Universal Heat Shield"; and U.S. Pat. No. 4,609,067, issued to Charles J. Gonwa on Sep. 2, 1986, entitled, "Heat Shield For A Vehicular Muffler". Both the Harter and Gonwa disclosures teach heat shields which are secured to a muffler by straps. Gonwa suggests that it is well known to weld a heat shield to a muffler body.
A typical method of welding a heat shield to a muffler shell is to make a series of discreet spot welds along the edge of each side of the heat shield to secure the heat shield to the shell. The utilization of spot welding is desirable inasmuch as it is a quick and efficient method of permanently securing the heat shield to the shell. However, prolonged use of the muffler often results in a problem in that some of the spot welds break, resulting in the heat shield having at least one edge freed from the shell to create an objectionable rattle.
The utilization of straps eliminates the breaking apart of spot welds; however, the added cost of providing the straps and applying the straps with the heat shield to the muffler shell increases the overall cost of the muffler assembly. It is therefore desirable to solve the problem of breaking spot welds s that it is not necessary to utilize straps.